The emissions reduction pledges made by individual countries through the 2015 Paris Agreement represent the current global commitment to mitigate greenhouse gas emissions in the face of the enduring climate crisis. Natural lands carbon sequestration and storage are critical for successful pathways to global decarbonization (i.e., as a negative emissions technology). Coastal vegetated habitats maintain carbon sequestration rates exceeding forest sequestration rates on a per unit area basis by nearly two orders of magnitude. These blue carbon habitats and their associated carbon sequestration benefits are vulnerable to losses from land-use change and sea-level rise. Incorporation of blue carbon habitats in climate change policy is one strategy for both maintaining these habitats and conserving significant carbon sequestration capabilities. Previous policy assessments have found the potential for incorporation of coastal carbon sequestration in national-level policies, yet there has – to date – been little inclusion of blue carbon in the national-scale implementation of Paris commitments. Recently, sub-national jurisdictions have gained attention as models for pathways to decarbonization. However, few previous studies have examined sub-national level policy opportunities for operationalizing blue carbon into climate decision-making. California is uniquely poised to integrate benefits from blue carbon into its coastal planning and management and its suite of climate mitigation policies. Here, we evaluated legal authorities and policy contexts addressing sequestration specifically from blue carbon habitats. We synthesized the progressive action in California’s approaches to mitigate carbon emissions including statutory, regulatory, and non-regulatory opportunities to incorporate blue carbon ecosystem service information into state- and local-level management decisions. To illustrate how actionable blue carbon information can be produced for use in decision-making, we conducted a spatial analysis of blue carbon sequestration in several locations in California across multiple agencies and management contexts. We found that the average market values of carbon sequestration services in 2100 ranged from $7,730 to $44,000 per hectare and that the social cost of carbon sequestration value was 1.3 to 2.7 times the market value. We also demonstrated that restoration of small areas with high sequestration rates can be comparable to the sequestration of existing marshes. Our results illustrate how accessible information about carbon sequestration in coastal habitats can be directly incorporated into existing policy frameworks at the sub-national scale. The incorporation of blue carbon sequestration benefits into sub-national climate policies can serve as a model for the development of future policy approaches for negative emissions technologies, with consequences for the success of the Paris Agreement and science-based decarbonization by mid-century.

各个国家通过2015年《巴黎协定》做出的减排承诺代表了当前全球在面对持续的气候危机时减少温室气体排放的承诺。天然土地的碳固存和储存对于成功实现全球脱碳途径（即作为负排放技术）至关重要。沿海植被生境的单位面积碳固存率比森林固存率高出将近两个数量级。这些蓝碳生境及其相关的碳固存效益很容易因土地用途变化和海平面上升而遭受损失。将蓝碳栖息地纳入气候变化政策是既要保持这些栖息地，又要保持重要的固碳能力的一种策略。先前的政策评估已经发现了将沿海固碳纳入国家级政策的潜力，但是迄今为止（迄今为止），几乎没有将蓝碳纳入国家范围的巴黎承诺的实施中。最近，作为脱碳途径的典范，地方司法管辖区引起了人们的注意。但是，以前的研究很少研究将蓝碳纳入气候决策的地方级政策机会。加利福尼亚拥有独特的优势，可以将蓝碳的收益整合到其海岸规划和管理以及一系列减缓气候变化的政策中。在这里，我们评估了专门解决蓝碳生境隔离问题的法律权威和政策环境。我们综合了加利福尼亚州减少碳排放的方法中的进步措施，包括将蓝色碳生态系统服务信息纳入州和地方级管理决策的法定，监管和非监管机会。为了说明如何产生可操作的蓝碳信息以用于决策，我们在加利福尼亚州多个机构和管理环境中的多个位置进行了对蓝碳固存的空间分析。我们发现，2100年固碳服务的平均市场价值在每公顷7,730美元至44,000美元之间，固碳价值的社会成本是市场价值的1.3至2.7倍。我们还表明，高固存率的小区域的恢复可以与现有沼泽的固存相比。我们的结果表明，有关沿海生境碳封存的可获取信息如何直接纳入地方以下规模的现有政策框架中。将蓝色碳固存收益纳入地方气候政策中可以作为开发未来负排放技术政策方法的模型，这将对《巴黎协定》的成功和到本世纪中叶的以科学为基础的脱碳产生影响。